Many if not most of the new HIV infections in the US are occurring among intravenous drug users (IDUs) and their sexual partners. Three types of programs have been shown to be effective in reducing HIV risk behaviors in this population: community outreach, drug abuse treatment, and syringe exchange programs (SEPs). National assessments of community outreach and drug abuse treatment programs have been conducted, but notably absent is a similar assessment of the state of SEPs in the US. The proposed research seeks to fill that gap. The proposed research addresses the following specific aims: (1) a description of the organizational characteristics of SEPs operating in the U.S. with a description of change in these programs over time; (2) an assessment of the demographic characteristics and risk behaviors of SEP participants; (3) the identification of individual-level factors associated with continued or persistent risk behaviors; (4) the identification of SEP organizational characteristics associated with risk among participants; (5) an examination of the relationships between SEP characteristics and change in risk behaviors among participants; and (6) an estimation of HIV incidence among participants in large SEPs. To achieve these aims, we will conduct annual telephone surveys of the directors of currently operating SEP in the US. This will provide current information on SEP implementation, organizational characteristics of SEPs, and services offered at SEPs. We will also conduct a stratified random sample of 25,920 interviews of participants in 6 large and 18 medium SEPs. The sampled programs will represent approximately half of all SE activity in the US. The sampling will be constricted to provide geographic representation and high versus low HIV seroprevalence rates among the IDUs served by the programs. Potential subjects will be randomly selected from persons visiting the SEPs. Data on demographic characteristics, drug use patterns and injection and sexual risk behaviors will be obtained. Audio-computer assisted structured interviewing, an innovative technique for increasing respondent privacy, will be used for SEP participant data collection. Our pilot study (grant R01 DA 09536) showed that this method can substantially reduce underreporting of HIV risk behavior. The proposed research will be the first national assessment of the state of syringe exchange programming in the US, and will use innovative data collection method to provide more complete reporting of HIV risk behaviors among SEP participants. The information obtained in the research should be useful for both HIV prevention planning in the US as well as understanding persistent risk behavior among persons already participating in prevention programs.